PLT-6763 Implement user access tokens and new roles (server-side) (#6972)

* Implement user access tokens and new roles

* Update config.json

* Add public post permission to apiv3

* Remove old comment

* Fix model unit test

* Updates to store per feedback

* Updates per feedback from CS

model/user_access_token_test.go

@@ -0,0 +1,58 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package model
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestUserAccessTokenJson(t *testing.T) {
+	a1 := UserAccessToken{}
+	a1.UserId = NewId()
+	a1.Token = NewId()
+
+	json := a1.ToJson()
+	ra1 := UserAccessTokenFromJson(strings.NewReader(json))
+
+	if a1.Token != ra1.Token {
+		t.Fatal("tokens didn't match")
+	}
+
+	tokens := []*UserAccessToken{&a1}
+	json = UserAccessTokenListToJson(tokens)
+	tokens = UserAccessTokenListFromJson(strings.NewReader(json))
+
+	if tokens[0].Token != a1.Token {
+		t.Fatal("tokens didn't match")
+	}
+}
+
+func TestUserAccessTokenIsValid(t *testing.T) {
+	ad := UserAccessToken{}
+
+	if err := ad.IsValid(); err == nil || err.Id != "model.user_access_token.is_valid.id.app_error" {
+		t.Fatal(err)
+	}
+
+	ad.Id = NewRandomString(26)
+	if err := ad.IsValid(); err == nil || err.Id != "model.user_access_token.is_valid.token.app_error" {
+		t.Fatal(err)
+	}
+
+	ad.Token = NewRandomString(26)
+	if err := ad.IsValid(); err == nil || err.Id != "model.user_access_token.is_valid.user_id.app_error" {
+		t.Fatal(err)
+	}
+
+	ad.UserId = NewRandomString(26)
+	if err := ad.IsValid(); err != nil {
+		t.Fatal(err)
+	}
+
+	ad.Description = NewRandomString(256)
+	if err := ad.IsValid(); err == nil || err.Id != "model.user_access_token.is_valid.description.app_error" {
+		t.Fatal(err)
+	}
+}